1. Field of the Invention
This invention relates to a method of providing temporary masking on electrical/electronic components and to compositions utilized in said method. Such compositions are photopolymerizable producing coatings with limited adhesive properties such that they provide a measure of adhesion sufficient to withstand component processing but insufficient to prevent easy mechanical removal of the coating. Typical applications include, but are not limited to, masking specific areas of printed circuit boards during soldering, plating or conformal coating operations.
2. Background Art
Heretofore, methods of providing printed circuit board protection have been limited to tape products and evaporative coatings.
The tape products as exemplified by Temp-R-Tape M727 and M737 from CHR Industries, Inc., are used by cutting to size and manually applying the tapes to the board. As such, these products do not lend themselves to automation and require a high level of labor input. Removal of the tapes is most often by peeling, although several water or solvent soluble versions are available on the market.
Evaporative products are typified by the masks available from Chemtronics, Inc., e.g., Chemask W, Chemask S, and Chemask Peelable. Such products are latex based and are applied to circuit boards as low viscosity liquids. Following board processing, the mask is removed from the board by peeling or washing in water or freon depending upon the grade. While it is possible to automatically apply such products to circuit boards, the long drying time required before a board can be further processed prohibits their use in high speed non-labor intensive production situations.
While photopolymerizable temporary masks are known in the electronics industry, their use has been as process aids in the development of permanent resists and polymer inner layers. It has never before been proposed to utilize a liquid photopolymerizable resist which can be mechanically stripped after photopolymerization.